The present invention relates to a gray scale mask, and particularly to a gray scale mask with slits and a light-blocking bar.
Currently, the manufacturing process of a thin film transistor liquid crystal display (TFT LCD) array substrate repeats thin film deposition, photolithography with a mask, and etching for several times. To reduce process period and save production time, a four mask (4Mask) technology has become introduced in manufacturing for replacing a conventional five (5Mask) technology. The implementation of the current 4Mask technology for mass production is to perform one masking process for both an active layer and a source/drain layer in patterning. After deposition of semiconductor layer and a source/drain layer, a gray scale mask (or gray tone mask) for example with slits and a light-blocking bar is used to perform a gray scale masking, so that the two masking processes for these two layers in the conventional 5Mask technology can be reduced to one masking process. The shape of the mask with slits and a light-blocking bar is for example shown in FIG. 8.
As shown in FIG. 8, the mask with slits and a light-blocking bar comprises a source mask region 1, a drain mask region 2, and light-blocking bar 4 arranged between the source mask region 1 and the drain mask region 2. In this structure, slits are formed between the source mask region 1 and the light-blocking bar 4 and between the drain mask region 2 and the light-blocking bar, respectively. As for the mask with slits and a light-blocking bar in the conventional technology, the photoresist in the gray scale region is not uniform in thickness, and the thickness of some photoresist in the gray scale region is so small that problems like the channel attack 7 in FIG. 9, the drain neck attack 8 in FIG. 10, and the like may occur. The channel attack 7 refers to a defect in which the portions between the ends of source mask region 1 and the drain mask region 2 depress. The drain neck attack 8 refers to a defect in which the neck of the drain mask region 2 depresses and the neck is narrowed. In either cases, the performance of the TFT changes or even deteriorates, which may influence the production quality.